1. Field of the Invention
The present invention relates to a toner development device for an electrophotographic copying machine, which is able to dissolve an unevenness in development by stirring developers composed of two kinds of components.
2. Prior Art
It is known in the art that it is desirable for the toner development device of above mentioned type to make both toner and carrier charged frictionally by mixing them well and also to feed the developers uniformly to dissolve the unevenness in development in the longitudinal direction of its photosensitive drum. Such device has so far been disclosed, for example in Japanese Utility Model publications of No. 27333 of 1975 and No. 31301 of 1982.
When feeding the developers to its magnet roller from the circulative loop passage defined by two screw rollers, it is intended for the developers to be stirred uniformly, respectively by two screw rollers of which screw directions are opposite to each other in the former publication of No. 27333 of 1975 and by two screw rollers of which screw pitches are different to each other in the latter publication of No. 31301 of 1982.
However, the toner development device in the above-mentioned prior art is apt to generate the unevenness in development length-wise along its photosensitive drum, particularly it is not easy to adjust for the dissolution of the unevenness in a large-sized copying machine. That is, upon the generation of any unevenness in development, first it becomes necessary to adjust the toner feed capacity of each screw roller, consequently the rotation speed of each screw roller. Therefor, it is required to provide a power transmission such as a gear box between one driving unit and the screw rollers or to provide a fine adjustment mechanism which makes use of two driving units in order to adjust each rotation speed of two screw rollers individually. Hence, these add substantially to the cost and complexity of the copying machine.
Even though once such fine adjustment was done, it might become necessary to readjust due to any displacement of the copying machine, an uneven surface of its installation floor or any balancing with the toner feed quantity, etc. And since this copying machine of the electrophotographic type has such peculiarity as developers are apt to be put aside in the circulative loop passage over a long time in use, it becomes difficult to readjust it under above described complex arrangement.